This medicine is a specific hormonal replacement therapy in the presence of hypothyroidism of any etiology.

Action And Clinical Pharmacology
Levothyroxine sodium is the monosodium salt of the levorotatory isomer of thyroxine (tetraiodothyronine), the principal hormone secreted by the normal thyroid gland.

Pharmacokinetics: Following oral administration, the absorption of levothyroxine is incomplete and variable (50 to 75%), especially when taken with food. Once absorbed, synthetic levothyroxine is indistinguishable from the endogenous hormone.

Levothyroxine is nearly totally bound to serum proteins and has an elimination half-life of 6 to 7 days in the euthyroid subject. Half-life is shortened in hyperthyroidism and prolonged in hypothyroidism and in pregnancy. Deiodination of levothyroxine (T4) to 1-triiodothyronine (T3) occurs in various tissues, particularly liver and kidney. T3 is approximately 4 times as potent as T4 on a weight basis.

The mechanism of action of thyroid hormones is not completely understood. The principle effect is to increase the metabolic rate of body tissues. Thyroid hormones have both catabolic and anabolic effects, and are therefore involved in normal metabolism, growth, and development, especially the development of the CNS in infancy.

Contra-Indications
Patients with hypersensitivity to any ingredient of the tablets and patients with thyrotoxicosis, acute myocardial infarction or uncorrected adrenal insufficiency. tag_WarningWarnings

Manufacturers' Warnings In Clinical States
Lactation: In euthyroid lactating mothers, levothyroxine (endogenous or exogenous) may be secreted into breast milk in amounts sufficient to mask signs of hypothyroidism in the nursing infant.

The use of levothyroxine in the treatment of obesity in patients who are not hypothyroid has been shown to be ineffective and potentially harmful.